docs: def _function(self, x, a, b, c, d, s):
          """Lorentzian asymmetric function
          x: frequency coordinate
          a: peak position
          b: half width
          c: area proportional parameter
          d: base line
          s: asymmetry parameter
          """
          return c/(np.pi*self._g_a(x, a, b, s)*(1.0+((x-a)/(self._g_a(x, a, b, s)))**2))+d